Mesopic and Scotopic Microperimetry and Multi-Modal Imaging in Eyes with Sub-retinal Drusenoid Deposits (SDD)

Abstract

 

Purpose

 

To evaluate the impact of SDD on cone- and rod-mediated vision in patients with age-related macular degeneration (AMD) using mesopic and scotopic microperimetry, and correlate the findings with retinal structures revealed by multimodal imaging including a new generation research adaptive optics scanning laser ophthalmoscope (UAB AOSLO).

 

Methods

 

Of 8 subjects enrolled, 3 patients had conventional drusen only, 2 patients had SDD only, and all had intermediate AMD (grade 6-7 on the AREDS 9-step severity scale). Three age-similar adults in good macular health served as controls. SDD and drusen were ascertained by presence in color fundus photographs, infrared, autofluorescence images, optical coherence tomography, and AOSLO. Cone- and rod-mediated sensitivity was tested using a microperimeter (MP1-S, Nidek) under mesopic and scotopic conditions. Subjects were tested 3 times on different days to assess the repeatability of rod-mediated testing since repeatability of MP1-S scotopic sensitivity has not been reported. MP1-S targets were overlaid on the AOSLO image in which the photoreceptor structure at the MP1-S test locations were examined (Fig.1).

 

Results

 

Compared to controls, subjects with drusen only showed similar cone- and rod-mediated light sensitivity, whereas those with SDD only showed reduced sensitivity for both cone- and rod-mediated vision (Table 1). MP1-S test targets with lower sensitivity corresponded to retinal areas more affected by SDD, as revealed by AOSLO. Mean rod-mediated sensitivity for the entire test region was similar on repeat testing (7.95 dB, 8.83 dB, and 9.39 dB), with correlations ranging from 0.64 to 0.74 (Pearson's r). The MP1-S’s 20 dB dynamic range of sensitivity creates a ceiling effect for cone- mediated testing in normal and AMD eyes with drusen only and a floor effect for rod-mediated testing in AMD patients with SDD only.

 

Conclusions

 

Microperimeters may be useful in assessing SDD’s impact on cone- and rod-mediated vision in patients with AMD. However, further visual function testing in additional patients using instruments with a larger dynamic range is warranted.  

 

Fig. 1 A, B, Cone- and rod-mediated light sensitivity.

 

 

Table 1, Mean (standard deviation) cone- and rod-mediated sensitivity (dB) tested at 68 points in the central 10° radius of macula with a Goldman size III target presented for 200 msec using a 4-2 threshold strategy.